An overshoot (OS) driving can be exemplified as a technique for driving a display panel in view of a gray scale transition. A conventional OS driving uses an OS table (LUT) similar to one shown in FIG. 24.
For example, when an input gray scale is 0 gray scale in a frame (hereafter referred to as a previous frame) which is one frame before a current frame and an input gray scale of the current frame (hereafter referred to as a subsequent frame) is 224 gray scale (target gray scale), an OS gray scale of 239 gray scale is outputted in the subsequent frame (see FIG. 14). This allows a display panel to have response waveform (transmittance change) as illustrated in FIG. 15. Note that “OTn” in the graph denotes a transmittance corresponding to an nth gray scale. When an input gray scale of a previous frame is 64 gray scale and an input gray scale of a subsequent frame is 224 gray scale (target gray scale), an OS gray scale of 235 gray scale is outputted in the subsequent frame (see FIG. 16). This allows the display panel to have response waveform as illustrated in FIG. 17.
When FIG. 15 and FIG. 17 are compared, although ultimate transmittances at their ends of the subsequent frame are identical to each other, the respective response waveform in one frame are remarkably different from each other. Therefore, when (i) a display, in which 64 gray scale is changed into 224 gray scale in one frame, is carried out in an area X and (ii) a display, in which 0 gray scale is changed into 224 gray scale in one frame, is carried out in an area Y adjacent to the area X, the area Y has only reached at most near OT 90 (transmittance corresponding to 90 gray scale) at the moment when the area X reaches near OT 224 (transmittance corresponding to 224 gray scale). When the respective response waveform in one frame thus differ from each other remarkably, an unnatural transient state such as one shown in FIG. 18 is visualized as jaggy at an image edge (moving image edge) of a moving image.
When an input gray scale of a previous frame is 224 gray scale and an input gray scale of the subsequent frame is 32 gray scale (target gray scale), an OS gray scale of 0 gray scale is outputted in the subsequent frame (see FIG. 19). This allows the display panel to have response waveform (transmittance change) as illustrated in FIG. 20. When an input gray scale of a previous frame is 128 gray scale and an input gray scale of the subsequent frame is 32 gray scale (target gray scale), an OS gray scale of 0 gray scale is outputted in the subsequent frame (see FIG. 21). This allows the display panel to have response waveform as illustrated in FIG. 22.
When FIG. 20 and FIG. 22 are compared, although ultimate transmittances at their ends of the subsequent frame are identical to each other, the respective response waveform in one frame are remarkably different from each other. Therefore, when (i) a display, in which 224 gray scale is changed into 32 gray scale in one frame, is carried out in the area X and (ii) a display, in which 128 gray scale is changed into 32 gray scale in one frame, is carried out in the area Y adjacent to the area X, an unnatural transient state such as one shown in FIG. 23 is visualized as jaggy at an image edge (moving image edge) of the moving image.
Patent Document 1 discloses the following technique to improve a response speed of a liquid crystal display apparatus. Three consecutive frames are indicated as (n−2)th frame through nth frame. Based on gray scales of the (n−2)th frame and the nth frame, a gray scale of the middle (n−1)th frame is corrected. Specifically, as illustrated in FIG. 25, in a case where the input gray scales of the (n−2)th frame through the nth frame are a black gray scale, a black gray scale, and a white gray scale, respectively, the gray scale of the (n−1)th frame is corrected to have a gray scale slightly lighter than the black gray scale. Then, a maximum gray scale is provided in the nth frame, thereby quickening the response in the nth frame. Thus, the white gray scale display is improved.
[Patent Document 1]
    Japan Unexamined Patent Publication, Tokukai, No. 2004-310113 (published Oct. 28, 2004)